Bob Smalser
01-08-2004, 4:37 PM
Ken can move or delete it if he chooses, but it was put here on purpose for those newcomers looking for a mortising machine.
In a small response to years of subtle but predatory marketing on PBS that has newcomers asking about mortising machines for their early projects, I prepared a short primer this morning in the shop to answer a younger man’s question. The entire session, including stock preparation and photography, took 30 minutes. The actual mortise chopping took 4 minutes, and I wrote this up on my lunch break.
First, you need mortise, not paring chisels. These Japanese ones below I bought from Highland Hardware when they first opened more than 2 decades ago to replace the badly worn family ones.
http://pic3.picturetrail.com/VOL12/1104763/3442941/42267813.jpg
Note the flat bevels in the photo above; not hollow ground and no secondary bevel. These are laminated blades designed for striking, and they come in the exact width of your intended mortise, ¼, 3/8, and ½ inches.
http://pic3.picturetrail.com/VOL12/1104763/3442941/42267803.jpg
Also note that the backs are hollow ground to facilitate easy flattening as you hone them during their life. You can see the hollow above the edge.
http://pic3.picturetrail.com/VOL12/1104763/3442941/42267831.jpg
Their bevels should be touched up on the hone every time you use them; your stones ready for use should be a permanent fixture on a corner of your bench. Honing these is easy; just index the flat bevel on the stone. You also need to hone the back dead flat, and I also hone the sides lightly on the fine stone to remove any burrs. I use a set of 4 Arkansas stones all the way to the finest “black” grade, but you can use what you normally sharpen with. I wiped the oil off the stone and chisel for clarity; don’t hone them dry or the stone’s pores will clog.
http://pic3.picturetrail.com/VOL12/1104763/3442941/42267823.jpg
I do a final stropping on the stitched muslin wheel with Knifemaker’s Green Rouge. Hard felt wheels are the best for this, but they are expensive.
http://pic3.picturetrail.com/VOL12/1104763/3442941/42268050.jpg
Then I lay out the mortises on the prepared stock. First, the mortise gage double tines are set to the width of this half-inch chisel. Then the mortise gage fence is set for mortise location on the stock, and lines scratched. Want to have the mortises dead center? Simple, just run the fence down the other face of the stock, compare the marks, and adjust the fence until the marks are identical.
http://pic3.picturetrail.com/VOL12/1104763/3442941/42268027.jpg
It’s a simple matter next to mark your mortise width with try square and marking knife. I’ll cut a simple blind double mortise and have used a pencil to make the lines clear in the photograph. You need to leave your pencils in the drawer for this and other joinery marking, as they are insufficiently precise.
http://pic3.picturetrail.com/VOL12/1104763/3442941/42268019.jpg
Index your mortise chisel plumb in the end knife cut, and strike with a wood mallet. Do all four ends.
Continued on Part II
In a small response to years of subtle but predatory marketing on PBS that has newcomers asking about mortising machines for their early projects, I prepared a short primer this morning in the shop to answer a younger man’s question. The entire session, including stock preparation and photography, took 30 minutes. The actual mortise chopping took 4 minutes, and I wrote this up on my lunch break.
First, you need mortise, not paring chisels. These Japanese ones below I bought from Highland Hardware when they first opened more than 2 decades ago to replace the badly worn family ones.
http://pic3.picturetrail.com/VOL12/1104763/3442941/42267813.jpg
Note the flat bevels in the photo above; not hollow ground and no secondary bevel. These are laminated blades designed for striking, and they come in the exact width of your intended mortise, ¼, 3/8, and ½ inches.
http://pic3.picturetrail.com/VOL12/1104763/3442941/42267803.jpg
Also note that the backs are hollow ground to facilitate easy flattening as you hone them during their life. You can see the hollow above the edge.
http://pic3.picturetrail.com/VOL12/1104763/3442941/42267831.jpg
Their bevels should be touched up on the hone every time you use them; your stones ready for use should be a permanent fixture on a corner of your bench. Honing these is easy; just index the flat bevel on the stone. You also need to hone the back dead flat, and I also hone the sides lightly on the fine stone to remove any burrs. I use a set of 4 Arkansas stones all the way to the finest “black” grade, but you can use what you normally sharpen with. I wiped the oil off the stone and chisel for clarity; don’t hone them dry or the stone’s pores will clog.
http://pic3.picturetrail.com/VOL12/1104763/3442941/42267823.jpg
I do a final stropping on the stitched muslin wheel with Knifemaker’s Green Rouge. Hard felt wheels are the best for this, but they are expensive.
http://pic3.picturetrail.com/VOL12/1104763/3442941/42268050.jpg
Then I lay out the mortises on the prepared stock. First, the mortise gage double tines are set to the width of this half-inch chisel. Then the mortise gage fence is set for mortise location on the stock, and lines scratched. Want to have the mortises dead center? Simple, just run the fence down the other face of the stock, compare the marks, and adjust the fence until the marks are identical.
http://pic3.picturetrail.com/VOL12/1104763/3442941/42268027.jpg
It’s a simple matter next to mark your mortise width with try square and marking knife. I’ll cut a simple blind double mortise and have used a pencil to make the lines clear in the photograph. You need to leave your pencils in the drawer for this and other joinery marking, as they are insufficiently precise.
http://pic3.picturetrail.com/VOL12/1104763/3442941/42268019.jpg
Index your mortise chisel plumb in the end knife cut, and strike with a wood mallet. Do all four ends.
Continued on Part II